1. Field of the Invention
This invention resides broadly in the field of electronic musical instruments, and is particularly adaptable for use in instruments employing a digital selection system for calling forth desired tones and voices from those available to be produced by the instrument. The principles of the present invention are applicable to electronic musical instruments in which musical sounds are generated in response to the actuation of key switches regardless of whether those switches are actuated directly, i.e., by the musician's fingers, or indirectly, by the plucking of strings. The term key is used in a generic sense, to include depressible levers, actuable on-off switches, touch or proximity responsive devices, closable apertures and so forth. The present invention relates to the characteristics of a musical note played on an electronic musical instrument. More particularly, the present invention relates to the transient voices which are dynamic in terms of amplitude and harmonics and often bear little resemblance to the final steady state tone normally associated with the instrument.
2. Description of the Prior Art
Heretofore, efforts to generate the characteristic transient voices of tones produced by electronic musical instruments have generally taken two approaches. The first approach employs a memory for storage of sampled waveform information to provide a single dynamically non-changing transient voice for the purpose of simulating chiff tone characteristics. Upon key actuation, the voice is read from memory and combined with other selected tones. This approach lacked flexibility since there could be no variation in voices during the transient time period. The second approach is to modulate the harmonic content of the transient voice as a function of time by computing in real time the amplitude contributions of constituent Fourier components. This system permitted amplitude and harmonic variation but does not utilize stored sampled amplitude waveform information.
In accordance with the present invention there is provided a method and apparatus for introducing variations in amplitude and harmonic content of the characteristic transient of tones produced in electronic musical instruments.